Inferior vena cava (IVC) filters are devices configured for insertion into the inferior vena cava to capture particles that may be present in the blood stream which, if transported to, for example, the lungs could result in serious complications and even death. Typically, IVC filters are utilized in patients who have a contraindication to anticoagulation or in patients developing clinically apparent deep vein thrombosis (DVT) and/or pulmonary embolism (PE). Patients who have recently suffered from trauma, have experienced a heart attack (myocardial infarction), or who have undergone major surgical procedure (e.g., surgical repair of a fractured hip, etc.) may develop clinically apparent DVT. When a thrombus clot loosens from the site of formation and travels to the lung, it may cause PE, a life-threatening condition. An IVC filter may be placed in the circulatory system to intercept one or more clots and prevent them from entering the lungs. IVC filters are either permanent or retrievable.
There are many different configurations for IVC filters, including those that include a central hub from which extend a plurality of struts that form filter baskets having a conical configuration, such as disclosed in U.S. Pat. No. 6,258,026, which is incorporated by reference in its entirety into this application. Other IVC filter configurations utilize wires and/or frame members to form straining devices that permit flow of blood while trapping larger particles. IVC filters are generally configured for compression into a small size to facilitate delivery into the inferior vena cava and subsequent expansion into contact with the inner wall thereof. The IVC filter may later be retrieved from the deployed site by compressing the legs, frame members, etc., depending on the filter configuration. Typically, an IVC filter will include hooks or anchoring members for anchoring the filter in position within the inferior vena cava. The hooks may be more elastic than the legs or frame members to permit the hooks to straighten in response to withdrawal forces, which facilitate withdrawal from the endothelium layer of the blood vessel without risk of significant injury to the vessel wall.
One type of hook or anchoring device for an endoprosthesis is shown in U.S. Pat. No. 5,843,167, in the form of an assembly that is attached to a graft. The assembly includes anchors which are attached to a graft on either end and which are connected by wire struts that extend along the length of the graft. These anchors have hooks that are formed on the end of short segments of wire that are secured to the anchor. The hooks are adapted to protrude radially outwardly upon deployment of the endoprosthesis, extending a short distance beyond the bends of the anchor. U.S. Pat. No. 5,843,164 discloses an anchoring system that includes hooks to penetrate a vessel wall. The hooks are generally provided at each end of a stent graft, each hook having one or more barbs thereon. U.S. Pat. No. 5,591,197 discloses a different type of anchor in the form of deformable connecting members that attach cylindrical elements which together form a stent. Upon balloon expansion of the connecting members, a notched, weakened area is forced outward to form a barb to penetrate a vessel wall. U.S. Pat. No. 5,593,434 discloses a plurality of projections or teeth cut away from a sheet of material, which is curled into a cylinder to form a stent. One possible drawback to these and other anchoring systems is that the teeth or hooks attached or integrated into the grafts or stents have a tendency to catch on the delivery sheaths or catheters during deployment. This creates problematic situations in the deployment process as the teeth or hooks tear the sheath material, preventing the necessary precision required in percutaneous delivery into a body lumen.
The following references relate to filters: U.S. Pat. No. 5,324,304; U.S. Pat. No. 6,972,025; U.S. Patent Application Publication No. 2003/0176888; U.S. Patent Application Publication No. 2004/0193209; U.S. Patent Application Publication No. 2005/0267512; and U.S. Patent Application Publication No. 2005/0267515, each of which is incorporated by reference in its entirety into this application.
Applicants have recognized that it would be desirable to provide an IVC filter that incorporates translating hooks, such that delivery to and from a body vessel is facilitated. Embodiments of such IVC filters are described herein.